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Gen Exam 1

Field of genetics that encompasses the basic principles of genetics and how traits are inherited

Molecular Genetics

Study of the chemical nature of genetic information and how it is encoded

Population Genetics

study of the genetic composition of populations and how a pop's collective group of genes changes with the passage of time

Model Genetic Organism

an organism that is widely used in genetic studies because it has characteristics , such as short generation time and large numbers of progeny, that make it well suited to genetic analysis

Pangenesis

Early concept of heredity proposing that particles carry genetic information from different parts of the body to the reproductive organs.

Inheritance Of Acquired Characteristics

early notion of inheritance proposing that acquired traits are passed to descendants.

Preformationism

early concept of inheritance proposing that a miniature adult resides in either the egg or the sperm and increases in size during developmentm with all traits beinf inherited from the parent that contributes to homunculus

Blending Inheritance

early concept of heredity proposing that offspring possess a mixture of of the traits from both parents

Cell theory

states that all life is composed of cells, that cells arise only from other cells, and that the cell is the fundamental unit of structure and function in livign organisms

Germ-plasm theory

states that cells in the reproductive organs carry a complete set of genetic information

Prokaryote

unicellular organism with a simple cell structure, include eubacteria and archea

eukaryote

organism with a complex cell structure including a nuclear envelope and membrane bounded organelles. 1 of the 3 primary divsions of life, include unicellular and multicellular forms

eubacteria

1 of the 3 primary divisions of life. consists of unicellular organisms with prokaryotic cells and include most of common bacteria

archaea

1 of the 3 primary divisions of life. archaea consist of unicellular organisms with prokaryotic cells

nucleus

space in eukaryotic cell that is enclosed by the nuclear envelope and contains the chromosomes

histone

low-molecular-weight protein found in eukaryotes that complexes with DNA to form chromosomes

Chromatin

material found in the eukaryotic nucleaus; consists of DNA and proteins.

homologous pair

2 chromosomes that are alike in structure and size and that carry genetic information for the same set of heredity characteristics. one inherited from the male parent and one from the female parent.

diploid

possessing two sets of chromosomes (2 genomes)

haploid

possessing a single set of chromosomes (one genome)

telomere

stable end of a chromosome

sister chromatid

2 copies of a chromosome that are held together at the centromere. each chromatid consists of a single DNA molecule.

cell cycle

stages through which a cell passes from one cell division to the next

interphase

period in the cell cycle b/w the cell divisions. In interphase, the cell grows, develops, and prepares for cell division

M Phase

period of active cell division; includes mitosis and cytokinesis

mitosis

process by which the nucleus of a eukaryotic cell divides

cytokinesis

process by which the cytoplasm of a cell divides

prophase

stage of mitosis. In prophase, the chromosomes contract and become visible, the cytoskeleton breaks down, and the mitotic spindle begins to form

metaphase

stage of mitosis, chromosomes algin in the center of the cell

anaphase

stage of mitosis in which chromatids seperate and move toward the spindle poles

telophase

stage of mitosis, chromosomes arrive at the spindle poles, the nuclear membrane re forms and the chromosomes relax and lengthen

meiosis

process in which chromosomes of a eukaryotic cell divide to give rise to haploid reproductive cells. consists of 2 divisions meiosis I and II

genetic factor that helps determine a trait. often defined at teh molecular level as a DNA sequence that is transscribed into an RNA molecule

allele

one of two or more alternate forms of a gene

Locus

Position on a chromosome where a specific gene is located

genotype

the set of genes possessed by an individual organism

homozygous

refers to an individual organism that posseses two identical alleles at a locus

heterozygous

refers to an individual organism that posseses two different alleles at a locus

phenotype

appearance of a characteristic

monohybrid cross

A cross b/w 2 individuals that differ in a single characteristic, a cross b/w individuals that are homo. for different alleles at the same locus (AA x aa) or (Aa x Aa)

P (parental) generation

first set of parents in a genetic cross

F1 (First Filial) generation

offspring of the initial parents in a genetic cross

F2 (Second Filial) generation

offspring of the F1 generation ina genetic cross

dominant

refers to an allele or a phenotype that is expressed in homozygous (AA) and in heterozygous (Aa)

recessive

refers to an allele or phenotype that is expressed only when homozygous

principle of segregation

important princicple of heredity discovered by Mendel that states that each diploid individual posseses 2 alleles at a locus and that these 2 alleles seperate when gametes are formed, 1 allele to each gamete

Concept of Dominance

Principle of heredity discovered by Mendel, when 2 different alleles are present in a genotype, only one allele may be expressed in the phenotype. The dominant allele is the allele that is expressed, amd recessive is not

Chromosome theory of inheritance

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Backcross

Cross b/w an F1 individual and one of the parental genotypes

Punnett Square

shorthand method of determining the outcome of a genetic cross. the gametes of one parent are written along the upper edge and the gametes of the other parent are written on left edge.

probability

likelihood of a particular event occuring; the number of times that a particular event occurs divided by the number of all possible outcomes. Prob. values range from 0 to 1

Multiplication rule

states that the probablity of 2 or more independent events occuring together is calculated by multiplying the probabilities of each of the independent events

addition rule

states that the probablity of any of 2 or more mutually exclusive events occuring is calculated by adding the probablities of the indiviidual events

test cross

a cross b/w an individual with an unknown genotype and an individual with the homozygous recessive genotype

incomplete dominance

refers to the phenotype of a heterozygous that is intermediate b/w the phenotypes of the two homozygotes

wild type

the trait or allele that is most commonly found in natural populations

Dihybrid cross

a cross b/w 2 individuals that differ in 2 characteristics, a cross b/w individuals that are homozygous for differnt alleles at the 2 loci (AABB x aabb) or ( AaBb x AaBb)

principle of independent assortment

genes encoding differnt characteristics seperate independently; applies only to genes located on different chromosomes or to genes far apart on the same chromosomes

goodness-of-fit chi-square

statistical test used to evaluate how well a set of observed values fit the expected values. The probablitly associated with chi value is the prob. that the differences b/w the observed and the expected values may be due to chance

pedigree

pictoral representation of a family history outlining the inheritance of one or more traits or diseases

chromosomes that differ morphologically or in number in males and females

autosome

chromosome that is the same in males and females; nonsex chromosome

heterogametic sex

the sex that produces 2 types of gametes with respect to sex chromosomes.

homogametic sex

the sex that produces gametes that are alike with regard to sex chromosomes

genic sex determination

sex determination in which the sexual phenotype is specified by genes at one or more loci, but there are no obvious differences in teh chromosomes of male or female

genic balance system

sex-determining system in which sexual phenotype is controlled by a balance b/w genes on the X chromosome and genes on the autsomes

X:A ratio

ratio of the number of X chromosomes to the number of haploid autosomal sets of chromosome; determines sex in fruit flies

turner syndrome

human condition where cells contain a single X chrom. and no Y chrom.(XO) They are female in appereance but do not undergo puberty and have poorly developed female secondary sex characteristics; most are sterile but have normal intelligence

klinefelter syndrome

human condition in which cells contain one or more Y chromosomes along with mutliple X chromosomes, people are male in appearance but frequently have small testes, slight breast enlargement, and reduced facial and pubic hair.

Triplo-X syndrome

human condition in which cells contain 3 X chromosomes. People with this have a female phenotype w/o dinstinctive features other than a tendency to be tall and thin.

sex-determining region gene

On the Y chromosome, a gene that triggers male development; also known as the testes deter. gene

sex-linked characteristic

char. develop. by a gene or genes on a sex chromosome

x-linked characteristic

char. deter. by a gene or genes on the x chrom.

Y-linked characteristic

char. deter. by a gene or genes on the Y chromosomes

hemizygosity

possession of a single allele at a locus. Males of organisms with XX-XY sex determination are hemizygous for X-linked loci,because their cells possess a single X chromosome.

dosage compensation

equalization in males and femaled of the amount of protein produced by X-linked genes.

barr body

condensed, darkly staining structure that is found in most cells of female placental mammals and is an inactivated X chromosome

lyon hypothesis

prposed by mary Lyon in 1961, this proposes that one X-chromosome in each female cell becomes inactivated (barr body) and suggests that which X becomes inactivated is random and varies from cell to cell.

Codominaance

type of allel interaction in which the heterzygote simultaneously expresses traits of both homozygotes

incomplete penetrance

refers to a genotype that does not always express teh expected phenotype. some individuals possess the genotype for a trait but do not express the phenotype.

penetrance

percentage of individuals with a particular genotype that express the phenotype expected of that genotype.

expressivity

degree to which a gene os expressed

lethal allele

causes the death of an individual organism, often early in development, and so the organism does not appear in the progeny of a genetis cross. recessive lethal alleles kill individual organisms rhat are homozygous for the allele; dominant lethals kill

lethal allle cont.

both heterzygous and homozygotes

multiple alleles

presence in a group of individuals of more than two allels at a locus. although, for the group the locus has more than 2 alleles, each member of the group has only two of the possible alleles.

gene interaction

interaction b/w genes at a differnt loci that affct the same characteristic.

epistatsis

type of gene interaction in which gene at one locus masks or supresses the effects of a gene at a differet locus.

epistatic gene

masks or supresses the effect of a gene at a different locus

hypostatic gene

gene that is masked or supressed by the action of a gene at a different locus

complementation test

test designed to deter. whether two differnt mutations are at the same locus. 2 individuals that are homozygous for 2 independently derived mutations are crossed.

complementation

2 different mutations in the heterzygous condotion are exhibited as the wild-type phenotype; indicates that the mutations are at a differnt loci.

sex-influenced charcteristic

encoded by autosomal genes that are more readily expressed in one sex. for example, an autosomal dominant gene may have higher penetrance in males than in females or an autosomal gene may be dominant in males but recessive in females

sex-limited charcterisitc

encoded by autosomal genes and expressed in onyl one sex. Both males and females carry genes for sex-limited char., but the char. appear in only one of the sexes.

cytoplasmic inheritance

inheritance of characteristics encoded by genes located in the cytoplasm. Because the cytoplasm is usually contributed entirely by only one parent, most cytoplasmically inherited char. are inherited from a single parent

genetic maternal effect

determines the phenotype of the offspring. with genetic maternal effect, an offspring inherits genes for the characteristics fvrom both parents, but hte offspring's phenotype is determined not by its own genotype but by the nuclear genotype of its mother.

genomic imprinting

differential expression of a gene that depends on the sex of the parent that transmitted the gene. if the gene is inherited from the father, its expression is differnt from that if it is inherited from the mother

epigenetics

phenomena due to alterations to DNA that do not include changes in the base sequence;often affect the way in which the DNA sequences are expressed. Such alterations are often stable and heritable in the sense that they are from one cell to the other.

temperature-sensitive allele

expressed only at certain temps

phenocopy

phenotype that is produced by environmental effects and is the same as the phenoycopy produced by a genotype

discontinous characteristic

exhibits only in a few, easily distinguished phenotypes. An example is seed shape in which seeds are either round or wrinkled

continous characteristic

displays a large number of possible phenotypes that are not easily distinguished, such as human height

quantitative characteristic

continous charcteristic; displays a large nu,ber of possible phenotypes, which must be described by a quantitative measurement